President Donald Trump’s top public health official resigned Wednesday amid mounting questions about financial conflicts of interest.

Dr. Brenda Fitzgerald’s resignation comes one day after POLITICO reported that one month into her tenure as CDC director, she bought shares in a tobacco company. Fitzgerald had long championed efforts to cut tobacco use, which is the leading cause of preventable death.

Fitzgerald, a doctor and former Georgia Department of Public Health commissioner, assumed leadership of the agency in July and was close to former HHS Secretary Tom Price, who resigned in September after POLITICO reported his use of private jets.

HHS Secretary Alex Azar, who was sworn in two days ago, accepted Fitzgerald’s resignation early Wednesday morning, according to a statement released by the agency.

“Dr. Fitzgerald owns certain complex financial interests that have imposed a broad recusal limiting her ability to complete all of her duties as the CDC Director,” said spokesman Matt Lloyd. “Due to the nature of these financial interests, Dr. Fitzgerald could not divest from them in a definitive time period. After advising Secretary Azar of both the status of the financial interests and the scope of her recusal, Dr. Fitzgerald tendered, and the Secretary accepted, her resignation. The Secretary thanks Dr. Brenda Fitzgerald for her service and wishes her the best in all her endeavors.”

An internal CDC email, shared with POLITICO, said the agency’s principal deputy director, Anne Schuchat, will assume the role of acting director immediately.

Democratic lawmakers seized on the news of Fitzgerald’s resignation. Sen. Patty Murray (Wash.), the top Democrat on the Senate committee that oversees public health, called it “unacceptable” that the former CDC director had such significant conflicts.

“It is unacceptable that the person responsible for leading our nation’s public health efforts has, for months, been unable to fully engage in the critical work she was appointed to do,” she said in a statement.

Democratic Rep. Louise Slaughter (N.Y.) said the CDC director’s resignation resulted from her 2012 law, which bars insider trading by members of Congress and other government employees and requires disclosures of their trading habits. POLITICO reporters used the STOCK Act to file for records of Fitzgerald’s transactions.

“This episode is exactly why I wrote this law and led the six-year fight to get it signed into law,” Slaughter said in a statement on Wednesday. “The American people deserve to know whether federal officials are upholding the public trust and adhering to the highest ethical standards, or using their powerful positions to enrich themselves.”

The resignation drew mixed reactions from health advocates who work closely with the agency.

“It’s just completely untenable — you can’t be the CDC director and buy stock in [tobacco companies] after you’ve been appointed,” said Emily Holubowich, executive director of the nonprofit Coalition for Health Funding.

In the wake of Price’s resignation, Holubowich said, and with Fitzgerald’s inability to divest of her other financial conflicts, the purchase of new tobacco stocks “broke the camel’s back.”

Carl Schmid, deputy executive director of the AIDS Institute, said he was disappointed by the news. “We had high hopes for her,” Schmid said, praising her public health background. He noted that she had not been as engaged as previous directors. “We never even had a chance to meet with her.”

Others said they were stunned and saddened by her departure.

“She was doing a good job of leading the CDC,” said Trust for America’s Health President and CEO John Auerbach, adding he’s “disappointed because the CDC’s work is extremely important and it needs to have support from the administration and from Congress.”

Former CDC Director Tom Frieden on Twitter wished her well and added that he hopes “the next director remains focused on using science to protect Americans from threats that arise in this country and anywhere in the world.”

It’s not clear who will replace Fitzgerald. The public health community, which tends to favor Democrats over Republicans, was supportive of her appointment and her background in public health. In the early days of the Trump administration, reality TV celebrity Dr. Mehmet Oz was rumored to be a contender for the job. And there was worry that Trump could appoint someone who would not strongly advocate in support of vaccines.

It’s unknown who Azar may want in the job next.

Jerome Adams – who has a good reputation on Capitol Hill – was in contention for the job last year but appears to be settling well into his job as surgeon general, according to sources familiar with his work.

A Republican state health official — such as Celeste Philip from Florida or John Dreyzehner from Tennessee — could be front-runners, according to sources in the public health world.

“I don’t know who Azar will bring in, but we really need some strong leadership at the CDC,” Schmid said.

Fitzgerald came to the job with a large, complicated stock portfolio that included hundreds of thousands of dollars in investments. She had stock in five other tobacco companies including Reynolds American, British American Tobacco, Imperial Brands, Philip Morris International and Altria Group, Inc., as well as a number of pharmaceutical stocks which she subsequently sold as part of her ethics agreement.

But the stock in Japan Tobacco was one of about a dozen new investments she made in the months after taking the helm of the agency, according to documents obtained by POLITICO. The purchase drew scrutiny from public health experts who said it goes against the mission of her agency and posed potential legal as well as ethical conflicts. She sold the tobacco stock at the end of October.

Fitzgerald had already come under congressional scrutiny for slow-walking divestment from the older holdings that government officials said posed potential conflicts of interest and prevented her from testifying before Congress. She and her husband have more than $300,000 in investments in GW Ventures and Greenway Messenger, which prevented her from testifying multiple times on cancer detection as well as on electronic health records that track the use of opioids, one of the nation’s biggest health crises.

Murray said she was “frustrated” when Fitzgerald canceled a second scheduled hearing.

Republican lawmakers were pressing her to sell the stocks so she could appear at hearings on Capitol Hill. Earlier this month, Fitzgerald assured GOP lawmakers that she was going to be able to sell her financial interest in the two companies, according to Sen. Lamar Alexander, the chairman of the Senate HELP Committee, and Sens. Richard Burr and Johnny Isakson.

Beside Japan Tobacco, Fitzgerald also purchased tens of thousands of dollars in new stock in at least a dozen companies, including between $1,001 and $15,000 each in Merck & Co, Bayer and health insurance company Humana, as well as between $15,001 and $50,000 in US Food Holding Co. in the months after she was appointed CDC director, according to financial disclosure documents.